1. Field of the Invention
This invention relates to a semiconductor device related to a full-wave rectifier circuit having a structure of a bridge composed of four diodes, specifically to a semiconductor device related to a full-wave rectifier circuit composed of high withstand voltage diodes.
2. Description of the Related Art
The full-wave rectifier circuit having a structure of a bridge composed of four diodes has been formed of a combination of low-price discrete diodes. However, it becomes necessary that the four diodes or the four diodes and related integrated circuit are formed in a single semiconductor die, in order to meet requirements such as overall size reduction of a product such as a portable device. In this case, careful consideration is required to integrate the diodes of high withstand voltage and high current in the single semiconductor die. For example, Japanese Patent Application Publication No. 2006-237210 discloses a method to prevent a junction breakdown in a portion of a semiconductor substrate which is outside a region where the bridge circuit is formed. According to the patent document, there is formed in the semiconductor die only the bridge circuit made of diodes formed side by side from both surfaces of the semiconductor die.
That is, two columns of a serially-connected pair of diodes are connected in parallel between two DC voltage output terminals in the bridge of a full-wave rectifier circuit. Therefore, a withstand voltage between the DC voltage output terminals of the semiconductor region other than the region in which the diodes are formed is required to be higher than twice a reverse breakdown voltage of the diode. Thus, three serially-connected diodes are formed in the semiconductor substrate and connected parallel to the serially-connected pair of diodes between the DC voltage output terminals. With that, there is disclosed the method to prevent the junction breakdown from occurring in the portion outside the region where the bridge circuit is formed by making the withstand voltage of the portion other than the region in which the serially-connected pairs of diodes are formed higher than the withstand voltage of the serially-connected pair of diodes.
Also, Japanese Patent Application Publication No. 2006-100308 discloses an example to form a full-wave rectifier circuit by forming diodes from only one of principal surfaces of a semiconductor die. An RF circuit, a memory circuit, a logic circuit and the like are incorporated in the semiconductor die. In this case, there is caused a problem that a parasitic transistor is fowled between elements that form the diodes. A countermeasure against the problem is disclosed.
That is, the Japanese Patent Application Publication No. 2006-237210 discloses only the full-wave rectifier circuit in which the four diodes are formed side by side from both surfaces of the semiconductor substrate to penetrate through the semiconductor substrate and connected to compose the bridge as described above. The Japanese Patent Application Publication No. 2006-100308 discloses the full-wave rectifier circuit made of the bridge circuit by forming the four diodes in only one of the principal surfaces of a P type semiconductor substrate.